A sprocket has a plurality of teeth are arranged on the outer peripheral part of the sprocket. In the case of a large sprocket used for a lower traveling unit of a tracked vehicle such as construction machine (e.g., hydraulic excavator, and bulldozer) and agricultural vehicle, even recent years, it is difficult to integrally form such a large sprocket with a plurality of teeth. For this reason, a plurality of sprocket segments corresponding to circumferentially divided parts of a sprocket are formed by forging. The sprocket is constructed of combination of the sprocket segments.
To form sprocket segments by forging, so-called vertically and horizontally stamping methods are known (see Japanese Examined Publication TOKUKO No. H03-39773 (published on June 14th HEISEI 3 (1991)), Japanese Utility Model Laid-Open Publication JITSUYO No. S60-181238 (published on December 2nd SHOWA 60 (1985), Japanese Utility Model Laid-Open Publication JITSUYO No. S60-181239 (published on December 2nd SHOWA 60 (1985), Japanese Examined Publication TOKUKO No. H03-41251 (published on June 21st HEISEI 3 (1991)), Japanese Examined Publication TOKUKO No. H03-41252 (published on June 21st HEISEI 3 (1991)), Japanese Patent Laid-Open Publication TOKUKAI No. S52-30994 (published on March 9th SHOWA 52 (1977), Japanese Examined Publication TOKUKO No. S58-17895 (published on April 9th SHOWA 58 (1983)), Japanese Patent Laid-Open Publication TOKUKAI No. H10-137890 (published on May 26th HEISEI 10 (1998)), Japanese Patent Laid-Open Publication TOKUKAI No. S60-102247 (published on June 6th SHOWA 60 (1985)) and Japanese Patent Laid-Open Publication TOKUHYO No. H07-501492 (published on February 16th HEISEI 7 (1995))). In the vertically stamping method, forming pressure is applied to a sprocket segment in a direction perpendicular to the tooth surface of the sprocket segment. In the horizontally stamping method, forming pressure is applied to a sprocket segment in a direction parallel to the tooth surface of the sprocket segment.